Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$231.57	3.564%	$239.8232	$239.82	$239.80	$239.80
Purchase #2	$76.61	8.230%	$82.915	$82.92	$82.90	$82.90
Purchase #3	$141.92	7.781%	$152.9628	$152.96	$152.95	$153.00
Purchase #4	$63.46	11.642%	$70.848	$70.85	$70.85	$70.80
Purchase #5	$37.46	12.329%	$42.0784	$42.08	$42.10	$42.10
Purchase #6	$183.47	6.854%	$196.045	$196.05	$196.05	$196.00
Purchase #7	$221.56	12.785%	$249.8864	$249.89	$249.90	$249.90
7 purchase totals =	$956.05		$1,034.5588	$1,034.57	$1,034.55	$1,034.50